Desulfurization and demtrogenizaiton



Uni f S ae PM 7 2,990,364 DESULFURIZATION AND DENITROGENIZATION OFCOAL TAR AROMATIC FRACTIONS Merrill J. Fowle,,Newtown Square, Paul M. Pitts, In, -Me dia, and Eugene Aristolf, Newtown Square, Pa, assignors toThe Atlantic Refining Company, Philaa delphia, Pa., a corporation of Pennsylvania NoDrawing. Filed Apr. 30, 1958, Ser. 'No. 731,875

I 2 Claims. (Cl. 208-209) This invention relates to a method for the desulfurization and denitrogenization of aromatic hydrocarbon-containing fractions produced from the destructive distillation 'of coal and more particularly this invention relates to a thermal conversion method for the removal ofsulfurcontaining compounds and nitrogen-containing compounds from aromatic hydrocarbon-containing fractions obtained from coal-tar light oil and coal-gas light oil.

The tars produced by the destructive distillation of coal contain major quantities of hydrocarbons and minor amounts of sulfur and nitrogen-containing compounds. For a number of years it has been the practice 'to distill from coal-tars a light oil fraction, generally a fraction boiling below about 400 F., containing substantial quantities of benzene, toluene, Xylenes and some higher molec ular weight alky-lated benzene hydrocarbons. In addition to these aromatic hydrocarbons, such light oil fractions contain rather large amounts of solvent naphtha which is composed of paraflins and more complex hydrocarbons.

During the destructive distillation of coal there-is also- When this coal-gas is scrubbed with so-called wash oils obtained produced coal-gas in rather large amounts.

from coal-tars rather large quantifies of benzeneQtoluene and xylenes are scrubbed from the coal-gas to produce a coal-gas light oil fraction which is highly aromatic. The

coal-tar light oil fraction and the coal-gas light oil-fraction form the preferred charge materials for the process of the instant invention. Each of these fractions will condrocarbons they may be treated by any of the well known commercial selective solvent processes to remove paraffinic constituents and to concentrate the aromatic content of such fractions. It has been found that the selective solvent treatment of these light oil fractions While removing paraffinic type constituents will remove only minor portions of sulfur-containing and nitrogen-containing compounds since the latter are in the form of hcterocyclic ring type compounds and therefore remain in the aromatic fraction. As has been pointed out, these light oil aromatic hydrocarbon-containing fractions generally boil below about 400 F., and accordingly are particularly suitable for thermal conversion processes since they may be vaporized rather easily.

It has been found that the thermal conversion of these light oil fractions to remove sulfur-containing and nitrogen containing compounds therefrom is best accomplished at temperatures ranging between 850 F. and 1350 F. at pressures in excess of 1000 pounds per square inch and ranging up to 10,000 pounds per square inch with reaction times in the range between 1 and 900 seconds and with an amount of hydrogen in the range between land moles of hydrogen per mole of hydrocarbon charge based on the average molecular weight of the hydrocar bon charge.

Somewhat more preferred reaction conditions employ temperatures in the range between 950 F. and

Q 1250" F., pressures between 2000 and.6000 pounds per square inch with reaction times in the range between 10 and 600 seconds and with amounts of hydrogen in the range between 2 and 10 moles of hydrogen per mole of hydrocarbon charge based on the everage molecular weight of the hydrocarbon charge. Under these conditions it has been found that from about 20 to 85 percent 'of'the sulfur contained in the charge may be removed in a single treatment while from 10 to 55 percent of the nitrogen contained in the charge may be removed simultaneously.

which involves thermal conversion in the presence of hy- I aromatic hydrocarbon containing fractions produced from the destructive distillation of coal by thermal conversion of such fractions in thepresence of hydrogen.

It is-a further object of this invention to pr'ovidea method for the desulfurization and denitrogenization of light oil fractions from coal-tar and coal-gas by thermal conversion of such light oil fractions in the presence of hydrogen.

Further objects of this invention will be apparent from the description and claims that follow.

In accordance with the instant invention the light oil fraction obtained by distillation from coal-tar or by scrub bing coal-gas with wash oil is subjected to thermal conversion in the presence of hydrogen to remove the sulfurcontaining compounds and nitrogen-containing compounds from such fractions. Since these light oil fractions contain rather large amounts of paraflinic type hy- The process hydrogen which may be suppliedentirely from an outside source is introduced into the process along with the charge hydrocarbons.- Since there'is a. small amount of hydrocracking of hydrocarbons in the process some hydrogen will be consumed 'and,of course, some hydrogen will be consumed in converting the sulfurcontaining compounds into hydrocarbons and hydrogen sulfide and the nitrogen-containing compounds into hydro,- carbons and ammonia. The hydrogen together with portions of the hydrogen sulfide and ammonia may be separated from the hydrocarbon eflluent by means of a conventional high pressure separator. The amounts of 'hydrogen sulfide and ammonia which will be separated from the hydrocarbons will depend, of course, upon the opera]? mg pressure of the high pressure separator. The hydrocarbon efiluent from the high pressure separator may then be flash stabilized to remove the low molecular weight hydrocarbons produced by hydrocracking. In addition to removing these normally gaseous hydrocarbons in the stabilizing operation, the residual hydrogen sulfide and ammonia likewise will substantially be completely removed leaving only the purified aromatic hydrocarbon fraction. The separation of hydrogen sulfide and ammonia from hydrocarbon streams may be accomplished by any one of several well known conventional methods and since such methods are not a part of this invention further discussion thereof is believed unnecessary.

The hydrogen which is separated from the hydrocarbon fraction may be recycled to the process without further treatment to remove any ammonia or hydrogen sulfide since these gases will reach an equilibrium concentration and not accumulate in the hydrogen. The use of recycle r 2,990, se4

hydrogen will, of-eourse, reduce the amount of make-up hydrogen required to. operate the, process. W p

The example which follows comprises a number of experiments designed to illustrate certain specific embodiments. of the invention.'

i Example 4 F. and shorter reaction times within the preferred condi- .tiqnsshquldheemplqye We claim: 1. A method for the desulfurization and denitrogenization of aromatic hydrocarbon-containing fractions produced from the destructive distillation of coal which comprises/subjectingsuch a fraction'solely. to thermal conversion in'theipresence of hydrogen at a temperature in the range' betWeen-SSO" Rand 1350 F., a-p ressure in excess oflQOO-poundsper-square inch and ranging up to 10,000

"pounds per square inch, for a time in the *rangebetween 1 and 900 seconds, the amount ofhydrogen ranging between 1.0 and 20-moles of hydrogen'per mole of hydrocarbon charge, and separating the hydrogen sulfide and ammonia produced during the conversion from the hydrocarbonproducts of the conversion reaction.

2. A method for-the desulfm'ization and denitrogenization of aromatic hydrocarbon-containing fractions produced from the destructive distillation of coal which com- Erpbrirhent N0 1 2 3 4 5 6 Conditions:

' "Temperature, F 950 950 1, 000 1,000 1,050 1, 100 Contact time, sec .150 i 30 150 300 300 600 Hydrogen to hydroca on mole j ratio"; 3:1 321 321 3:1 3:1 '3:1

Liquid-Reeoverymt. percent- 98. 8 94. 2 97. 3 92. 7 90; 4 39. 3

UonipmiHydrocai-bon'Produetpwt. percent no loss 7 basis Charge No. 1 No.2 No.3 No.4

. ...':C 'to-O; para-fins ,1.1 as 2.6 7. 2 as 10.6 .0 anddieavier parafiins,

cycloand dicy'clopara- :flinsfl 4. 1' 4. 8 2.6 1.8 3.8 2.8. 0. 4

56.3 66.1 55.7 53.2; eats sro zone 10. 9 10. 4 11. 4 9. 7 5. 4 1. 3 --Heavier alkylated zenes 4.1 3.5 .2.8 3.8- 28 7 L0 0.4 Average mol wt. of aromatics- -s7.1 85.5 86.0 86. 7 86.0 33.0' {vars Wt. percent sulfur in liquid 0; as o. 23 0. 23 0. 22 0. 0.06 one wt.-peroentnitrogen inliquid. M 0:04 0. 031 0.027' 0. 028 0. 024 0. 036 0. 018 Wt. percent desuliurizatiom. 2O 34 ;37.. .43 -83.'. -83 Wt. percent; denitrogenizt rtinn 1 22 32- 40 "10 55 These'data show that substantial'amounts of the sulfurcontaining and nitrogen-containing compounds may "be removed-inn single pass through thereactor. These 'data also show that if-theprimarypurpose of the thermal con- Nersiontreatment-is to-remove sulfur-containing and nitrogen-containing-compounds Without substantially changing the a-romatic hydrocarbon distribution long reaction times and temperatures below about-1050. F. shouldbe employed. Stated inother words, within thepreferr'edre- .If, tothe contrary, it -is-desired not onlyto remove the sulfur-containing compounds and nitrogen-containing cpmpoundsbutalsoto convert the other aromatic-hydrocarbons to benzene, then temperatures above about 1050" prises -subjecting such a fraction solely to thermal ,conversion'in the presence of hydrogen at a temperature in the range between'950 'F. and 1250 F., apressure of from 2000 to 6000 'pounds per square inch, for a time in therange between 10 and'600 seconds, the amount of hydrogen ranging between 2 and 10 moles of hydrogen per'mole of hydrocarbon charge, and separating the hyd rogen sulfide and ammonia produced during the conversion firom thehydrocarbon products of the conversion reaction.

References 'Cited'in the file of this patent UNITED STATES PATENTS 2,705,733 Nonnenmacher et-al. Apr.;5, 1-955 30 2,706,209 Reitz et a1. n Apr. '12, 1955 2,708,180 Fuener etal. .,May 10, 1955 2,83,441 Sawyer Apr. 21, 1959 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2390 364 June 27 1961 Merrill J9 Fowle et all,

it is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3 line 3 for "comprises" read compares Signed and sealed this 21st day of November 1961.,

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents USCOMM-DC 

1. A METHOD FOR THE DESULFURIZATION AND DENITROGENIZATION OF AROMATIC HYDROCARBON-CONTAINING FRACTIONS PRODUCED FROM THE DESTRUCTIVE DISTILLATION OF COAL WHICH COMPRISES SUBJECTING SUCH A FRACTION SOLELY TO THERMAL CONVERSION IN THE PRESENCE OF HYDROGEN AT A TEMPERATURE IN THE RANGE BETWEEN 850* F. AND 1350* F., A PRESSURE IN EXCESS OF 1000 POUNDS PER SQUARE INCH AND RANGING UP TO 10,000 POUNDS PER SQUARE INCH, FOR A TIME IN THE RANGE BETWEEN 1 AND 900 SECONDS, THE AMOUNT OF HYDROGEN RANGING BETWEEN 1.0 AND 20 MOLES OF HYDROGEN PER MOLE OF HYDROCARBON CHARGE, AND SEPARATING THE HYDROGEN SULFIDE AND AMMONIA PRODUCED DURING THE CONVERSION FROM THE HY-AND DROCARBON PRODUCTS OF THE CONVERSION REACTION. 